In the food processing industry it is often desirable to separate agricultural products into a number of grades based on the size of the product. Grading is often necessary to comply with regulatory or customer demands for general uniformity in product size. Furthermore, a premium price may be obtainable for agricultural products of a desired size. Smaller beans, for example, command a higher price than larger ones by weight.
One known grading apparatus utilizes an inclined rotatable drum having a cylindrical wall comprised of alternating fixed and rotatable bars. Each rotatable bar has a width which is greater than its height such that spacing between each rotatable bar and The two adjacent fixed bars may be adjusted by rotation of the bar. To obtain uniform grading it is important that the spacing between all rotatable bars and the fixed bars be constant at a desired setting. In this known apparatus spacing is controlled by a frustoconical cam which bears against cam following rollers which are attached to each rotatable grader bar at the grader inlet. This cam has a recessed portion at the top of the drum travel which causes the grader bars to open to their wider spacing to release food product which has become trapped between grader bars. In order to retain the grader bar cam followers engaged against the cam each individual cam follower is provided with a coil spring which extends between the cam follower arm and the drum end plate.
As a typical grader may employ 30-50 rotatable grader bars and rollers, a great number of coil springs are required. Furthermore, the constant flexing to which the springs are subjected will result in eventual spring failure. The failure of one spring may not be immediately obvious to the grader operator yet will result in the improper grading of the processed food product.
What is needed is a grader for agricultural products having cam followers which are consistently engaged against the cam, which employs a minimum of parts, and which provides immediate visual indication of failure.